FIG. 19 depicts an example of the related art heat cooking device. A thermistor 102 is provided in the vicinity of the center of IH coil 101. This heat cooking device is arranged such that the surface temperature of a cooking tool 103 placed on a top plate 104 is indirectly detected by the thermistor 102. During automatic water boiling process, the heat cooking device lowers the caloric force stepwise from a high value to a low value via a middle value as the temperature detected by the thermistor 102 rises. When the percent change of detected temperature at a low caloric force becomes smaller than predetermined criterion, water boiling is then detected.
As another background art, there is disclosed in JP-A-2003-139385 a bath temperature detecting device for obtaining the temperature of hot water in a bath tub comprising an electric supply unit, a temperature detecting unit of detecting the temperature of hot water in the bath tub and a transmitting unit of wireless-transmitting the temperature data thus detected to the bath system.